1. Field of the Invention
This invention relates to disc-type valves as used, inter alia, in industry in flow lines or pipe lines to control the flow of gaseous and fluid materials in pipelines.
2. Description of the Prior Art
Disc-type or plate valves, as commonly used in industry generally comprise four main components, to wit, a tubular body, a flange or seat circumferentially mounted within the tubular body, a disc or plate or plate with a peripheral seal mounted thereto, and an operating mechanism to move the discs from a position against the seat to a position generally parallel to the flow path of material transversing the valve. The conventional disc valves incorporate operating mechanisms which merely transversally move the disc in a 90.degree. arc from against the seat and back again to close the valve. Because the edge of the disc cannot be pushed through the seat, the pivotal center of this arc cannot be transversally on the disc but, rather, must be offset away from the plane of the seat. Thus the whole disc travels through an arc rather than merely pivoting about a transverse axis. A valve such as this is shown in British Pat. No. 405,439 to Dick et al.
Referring to the Dick et al British Patent, it will be noted that as the disc arcs away from the seat, the upper edge of the disc, in particular the seal about that area, is caused to slide or drag across the seat as the disc moves out of parallel with the seat. Such slide or drag causes a propensity for wear on both the seat and the seal.
The seals in these types of valves, must be somewhat flexible to permit them to conform to the inherent surface irregularities of metal seats. Seals generally are formed of either a synthetic elastomer, for example, silicone rubber, or a soft metal such as series 1100 aluminum or OFHC copper where operating temperatures are too high for elastomers. None of the available seal materials are particularly wear resistant and, thus, deteriorate rapidly in valves which operate generally as shown in the Dick et al British Patent.
Disc-type valves have been developed which overcome the problem of seal and seat abrasion by linearly retracting the disc from the seat before beginning the arc movement. Such valves are shown in U.S. Pat. No. 4,073,470 to Harris and U.S. Pat. No. 4,073,472 to Chasey. However, there is another problem with these newer valves. Since the valve disc and the interior of the valve are enclosed, a person operating the valve is unable, under normal operating circumstances, to view the inside of the valve. The degree of rotation of the operating shafts of these valves does not bear a direct one-to-one relationship with the degree of arc movement of the disc. Thus it is difficult for the operator to readily determine how far open or closed the disc is when he wants to regulate the flow of material passing through the valve as distinguished from either fully opening or completely closing the valve. This problem is also present in the valve disclosed in British Patent No. 405,439.
The object of the present invention is to incorporate both a lateral movement of the disc in relation to the seat, so as to prevent seal and seat abrasion, and to provide a positive, easily deteminable means to regulate material flow through the valve.